1. Technical Field
The present invention relates to cellulose ester films, and polarizing plates and liquid crystal displays comprising such cellulose ester films. For more details, the present invention relates to cellulose ester films having high transmittance, and polarizing plates with less deterioration at the time when durability is tested and liquid crystal displays having high contrast, both of which comprise such cellulose ester films.
2. Description of Related Arts
Liquid crystal displays (LCDs) have been widely used in late years because they have been getting thinner, and have had lighter weight and less power consumption. In particular with regard to lightweighting, measures to make components more power saving and thinner have advanced. Additionally, it has been recently demanded to achieve new functions such as still lower power consumption or 3D. For both of the lower power consumption and 3D, improved utilization efficiency of light is required. To that end, it is considered to use LED as a backlight and to increase the transmittance of the component. When it comes to the transmittance of the component, it is considered to lessen the gaps of ribs, slits and the like for liquid crystal cells and to increase the transmittance for films.
For example, to increase the transmittance of the film, it is considered to thin the film thickness. Yet, in the case of retardation films, making the film thinner leads to difficulties in developing retardation, which has been problematic.
In view of this, retardation films using cellulose esters with a lower degree of substitution were proposed (see, for example, Patent Document 1). Yet, there were problems of low transmittance of the film and poor compatibility with retardation.
Further, retardation films using cellulose esters with a lower substitution degree and carbohydrate organic esters were proposed (see, for example, Patent Document 2). Yet, in the case of monosaccharide esterified products, the polarizing film might have a less capability to inhibit shrinkage (shrinkage inhibiting capability) particularly when made to a thin film. Furthermore, when retardation films using cellulose esters with a lower substitution degree and carbohydrate organic esters were subjected to rework (see, for example, Patent Document 3), although the retardation is high, there occurred a defect of polarizing plates scattering into strips or splitting off to leave liquid crystal cells.